Metamorphic Evolution of the Ribeira Belt: Evidence from Outcrops in the Rio de Janeiro Area, Brazil |
| |
| Authors: | KUHN A; STUWE K; TROUW R A J |
| |
| Institution: | 1 DEPARTMENT OF GEOLOGY AND PALAEONTOLOGY, UNIVERSITY OF GRAZ, HEINRICHSTRASSE 26, 8010 GRAZ, AUSTRIA
2 UNIVERSIDADE FEDERAL DO RIO DE JANEIRO, DEPARTAMENTO DE GEOLOGIA, CEP 21910-900 RIO DE JANEIRO, BRAZIL |
| |
| Abstract: | Migmatitic granulites and arc-related felsic intrusives of Pan-Africanage form the bedrock in the Rio de Janeiro area, SE Brazil.These rocks preserve a partial record of three parageneses.The earliest assemblage (M1) grew during fabric formation inthe rocks (D1) and is characterized by the mineral assemblagePl + Bt + Sil + Kfs + Qtz. Peak metamorphic conditions (M2)are characterized by the assemblage Bt + Crd + Kfs + Pl + Grt+ liq + Qtz and are inferred to have developed during D2 foldingof the rocks at T = 750–800°C and P = 7 kbar. M3 reactiontextures overprint the M2 assemblage and comprise symplectiticintergrowth of cordierite(II) and quartz that formed after garnet,whereas secondary biotite formed as a result of reactions betweengarnet and K-feldspar. By comparing the observed modal abundanceswith modal contours of garnet, cordierite and quartz on therelevant pseudosection a post M2 P–T vector indicatingcontemporaneous cooling and decompression can be deduced. Theinferred equilibrium assemblage and reaction textures are interpretedto reflect a clockwise P–T path involving heating followedby post-peak decompression and associated cooling. We inferthat metamorphism occurred in response to advective heatingby the abundant syn-collisional (arc-related) I-type granitoidsin the region, consistent with the unusually high peak T/P ratio. KEY WORDS: advective heating; Ribeira belt; granulite; partial melting; P–T pseudosection |
| |
| Keywords: | : advective heating Ribeira belt granulite partial melting P– T pseudosection |
| 本文献已被 Oxford 等数据库收录！ |
|
